Compressor superheat switch with bellows mounting ring

ABSTRACT

A simple and easily assembled pressure and temperature responsive switch having a bellows type actuator and especially adapted to be used in an automobile air conditioning system. The switch assembly includes a sealed bellows supported within an annular mounting ring which is adapted to be inserted within a recess in the head of the compressor. A cup-shaped housing member is inserted in the recess over the mounting ring and sealed with respect to the surrounding wall of the recess to prevent refrigerant leakage therefrom. The housing member supports an insulated electrical contact which is supported adjacent the mid portion of the bellows to complete an electrical indicator circuit when the bellows expands in response to a predetermined high temperature or low pressure of refrigerant.

United States Patent [191 Watt [ COMPRESSOR SUPERI-IEAT SWITCH WITH BELLOWS MOUNTING RING 75 lnventor: Roy E. Watt, Brooltville, Ohio [73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: May 7, 1973 [2]] Appl. No.: 357,593

[52] US. Cl 200/83 N, 337/320, 200/83 D, 73/407 R [51] Int. Cl. H0lh 35/32 [58] Field of Search... 200/83 R, 83 A, 83 D, 83 N, 200/83 S, 83 SA, 61.25; 73/406, 407 R, 407 PR; 337/320, 321

[451 May 7,1974

Primary Examiner-Robert K. Schaefer Assistant Examiner-Gerald P. Tolin Attorney, Agent, or Firm-K. H. MacLean, Jr.

[5 7] ABSTRACT A simple and easily assembled pressure and temperature responsive switch having a bellows type actuator and especially adapted to be used in an automobile air conditioning system. The switch assembly includes a sealed bellows supported within an annular mounting ring which is adapted to be inserted within a recess in the head of the compressor. A cup-shaped housing member is inserted in the recess over the mounting ring and sealed with respect to the surrounding wall of the recess to prevent refrigerant leakage therefrom. The housing member supports an insulated electrical contact which is supported adjacent the mid portion of the bellows to complete an electrical indicator circuit when the bellows expands in response to a predetermined high temperature or low pressure of refrigerant.

3 Claims, 5 Drawing Figures This invention relates generally to air conditioning systems and more particularly to a pressure and temperature responsive indicator switch adapted to be mounted in the compressor.

In air conditioning systems of the type which utilize a compressor to pressurize refrigerant, oil for lubricating the compressor is normally mixed with the refrigerant for passage through the system with the refrigerant. The oil collects in a sump portion of the compressor for subsequent lubrication of moving parts of the compressor. When the refrigerant charge in the air conditioning system is fully charged, enough oil will be distributed in the sump region of the compressor to properly lubricate the compressor. However, when the charge level of refrigerant is reduced for instance by leakage, some of the oil will be pumped out of the compressor and collected in other parts of the system such as the evaporator. If the refrigerant charge is very low, not enough refrigerant will circulate to return oil to the compressor for proper lubrication. For example, it has been observed that in an air conditioning system normally charged with about 4 lbs. of freon refrigerant, a reduction to about 1 lb. of refrigerant usually causes insufficient lubrication of the compressor.

When an air conditioning system is operated with an insufficient refrigerant charge, the superheat temperature of refrigerant in the suction line or intake of the compressor will be increased (superheat is the temperature of fluid above its saturation temperature at a given pressure). Another effect is a marked decrease in suction line pressure under most operating'conditions.

The present invention includes an improved temperature and pressure responsive superheat switch adapted to be mounted within a recess in a compressor housing. When on, the switch'completes an indicating or warning circuit in response to high refrigerant temperature or low refrigerant pressure. The superheat switch includes a refrigerant charged bellows which has two circular members jointed together at their peripheral edges to form a sealed space therebetween. The refrigerant within the space is capable of exerting a pressure force against the bellows which causes one end of the bellows to move away from the other and to engage an electrical contact to complete the warning circuit.

The switch is composed of several elements which are easily assembled. The bellows is gripped within an annular mounting ring having an inner bore with a groove therein into which the bellows is snap-fitted.

The mounting ring and bellows may be preassembled and then inserted into a recess in the compressor head. It is held therein by a cup-shaped housing member which is also inserted into the recess. The housing member is retained therein by an annular expansion ring which engages a groove in the compressor housing. An O-ring seal between the housing member and the compressor prevents refrigerant leakage thereby. The annular mounting ring also includes circumferentially spaced passage means to permit refrigerant flow around the edge of the bellows to place both bellows surfaces in good heat transfer relationship to the refrigerant to expose both surfaces to refrigerant pressure.

The housing member supports an insulated contact in circuit with an indicating means to energize the same when the bellows expand to engage thecontact. It is important that the bellows and the contact be spaced a predetermined distance apart as a predetermined assembly temperature so as to operate correctly upon sensing a predetermined low refrigerant pressure and high refrigerant temperature corresponding to a low refrigerant charge. The subject switch assembly makes calibration easy during assembly by the insertion of shims between the bellows mounting ring and the contact carrying housing member to properly space the contact and bellows.

Therefore, an object of the invention is to provide a temperature and pressure responsive switch adapted for simple mounting within a recess in a compressor and including a bellows member supported within an annular mounting ring which itself is insertable in the recess.

A further object of the invention is to provide a temperature and pressure responsive switch for mounting within a recess in a compressor which is easily assembled and calibrated by first inserting a mounting ring bellows subassembly within the recess, next inserting shims over the mounting ring, inserting a cup-shaped housing member over the shims and finally installing a radially expandable retainer into the recess to engage a groove.

Further objects and advantages of the present invention will be more readily apparent from the following detailed description, reference being had to the accompanying drawings in which a preferred embodiment of the present invention is clearly shown.

IN THE DRAWINGS FIG. 1 is a schematic view of an air conditioning system including the improved superheat switch;

FIG. 2 is an enlarged sectional view of the improved superheat switch;

FIG. 3 is an enlarged detail view of the superheat switch shown in FIG. 2;

FIG. 4 is a vertical sectioned view of the mounting ring which supports the bellows shown in FIG. 2; and.

FIG. 5 is a perspective view of the mounting ring also shown in FIG. 4.

In FIG. 1 of the drawings, an air conditioning system is shown including a compressor 10 having a pulley drive assembly 12 mounted upon the end of the compressor. The pulley assembly 12 is connected for rotation therewith to the drive shaft of the compressor (not visible) by magnetic means actuated by energization of a coil 14. The coil 14 is in circuit with a battery 16, one terminal of which is grounded by a conductor 18, the other terminal of which extends through conduit 20 to an ambient switch 22 which closes at ambient temperatures above a predetermined value such as about 40 F. The ambient switch 22 is in turn connected by a conduit 24 to a master ON/OFF air conditioning switch 26 which is conveniently located in the passenger compartment of an automobile for manual operation. A conductor 28 connects the switch 26 with a fuse 30 with a capacity to provide adequate current to coil 14 through conductors 32 and 34.

Going back to the refrigerant system, the compressor 10 has an outlet 36 connected by a conduit to the inlet 38 of a condenser 40. The condenser is normally loconnected by a thin tube 52 to the valve 48. The bellows 50 responds to temperature changes and moves a valve element (not visible) in the valve 48 to regulate the flow of refrigerant through the expansion valve 48. An outlet 54 of expansion valve 48 ,is connected to the inlet 56 of an evaporator 58. The evaporator 58 is positioned in a flow of air into the passenger compartment for cooling purposes. Heat is absorbed from the air as it passes through the evaporator and this causes the refrigerant within the evaporator to vaporize. The vaporized refrigerant then passes from evaporator 58 through an outlet 60 to a throttling valve means 62. The throttling valve 62 senses refrigerant pressure at the outlet of the evaporator and controls the discharge of refrigerant from the evaporator to maintain refrigerant pressure therein above a predetermined value to prevent frost formation on the evaporator surfaces. Re-

frigerant then flows from the throttling valve 62 through a conduit 64 to an inlet 66 of the compressor 10. The aforedescribed refrigerant system is set forth as an example of a well known and used compressed refrigerant type air conditioning system.

This invention relates to an improved superheat switch 68 which is shown in FIG. I mounted in the compressor 10. Details of the switch 68 are best illustrated in FIG. 2. It is supported within a recess 70 in the end head 72 of compressor 10. The switch'includes a circular bellows actuator 74 formed by two substantially planar or sheets surfaces 76 and 780i thin-walled material. The sheets 76, 78 are joined at their outer edges 80 and 82 to enclose an interior space 84 therebetween. A fill tube 86 is sealingly attached at 88 through one of the sheets 76. The fill tube 86 has an inner bore 90 used to charge the interior space 84 of the bellows 74 with a thermally expansive material such as refrigerant-The outer end 92 of the tube is crimped subsequent to the fill operation and soldered at94 to prevent refrigerant leakage from interior 84.

The outer edge 82 of bellows 74 is supported and encircled by a mounting ring 96 as best shown in FIG. 5. The mounting ring 96 is adapted to be inserted within recess 70 and to be pressed against the bottom 98 of the recess. The mounting ring is shown by itself in FIGS. 4 and and includes an inner bore 100 for receiving the peripheral edge 82 of bellows 74. A lip portion 102 which extends radially inward from the outer portion of the mounting ring 96 provides axial support for the bellows 74. An annular groove 104 within the bore 100 is adapted to grippingly engage the curved edge of the bellows 74. The subassembly of the bellows 74 and the mounting ring 96 may be conveniently formed prior to the final assembly in a compressor.

When assembled; the mounting ring 96 is inserted within recess 70 and bellows 74 is supported across the opening formed by the bore 100. Radial slots 106 in the mounting ring 96 permit refrigerant to flow around the periphery of the bellows 74 and to bathe or wash substantially all of its surface area to provide good heat transfer between the refrigerant and the bellows 74.

A cup shaped circular switch housing 108 is adapted to be inserted within recess 70 over the mounting ring 96 and held therein by a radially expandable retainer 110. The switch housing 108 is encircled by an O-ring seal 112 within a groove 114 to prevent refrigerant leakage therebetween from the interior inlet portion 115 of the compressor. The housing 108 supports a contact pin 116 which is mounted within an electrical insulating material such as glass 118. The contact pin 116 extends into the interior 120 of assembly 68 toward a cotnact pad 122 supported on surface 78 of bellows 74. The contact pin 116 is externally connected by a conductor 124 shownin FIG. 1 to a warning light 126 which is connected by a conductor 128 to the fuse 30.

The contact pin 116 extends toward contact pad 122 supported upon the surface 78 of bellows 74. When' refrigerant within the interior 84 of bellows 74 experi- K ences volumetric expansion caused by temperature increases or pressure decreases in inlet portion 115, the surface 78 is moved with respect to surface76 and will eventually cause pad 122 to engage the contact pin 116. This completes the warning or indicating circuit including battery 16, fuse 30, light 126.If the indicator light 126 remains on for any appreciable length of time, this makes the vehicle operator aware that the refrigerant charge in the air conditioning system is probably depleted by leakage or some other cause to an insufficient level to provide proper cooling and'lubrication of the compressor 10. Thereby, the operator is advised to de-energize the air conditioning system by opening the master ON/OFF switch 26.

As has been explained, the improved switch'assembly is simple in construction. In addition it is easily assembled and calibrated at the same time. First, the subassembly including mounting ring 96 and bellows assembly 74 is inserted within recess70. Next, one or more pre-selected shim means 132 in the form of annular metal rings are inserted over the mounting ring 96. The housing 108 is then inserted into the recess and against the O-ring 112. Finally, retainer is expanded into groove 134 in a compressor housing 72 to hold the switch assembly 68 within ,the recess'70.

Calibration of the switch 68 is conveniently made during assembly by determining the extension of the mounting ring and bellows assembly 74 at a predetermined temperature. Next, shims 132 of necessary thicknesses to provide proper spacing of pad 122 and pin 116 are inserted between the housing 108 and mounting ring 96.

While theembodiment shown in the drawings and described above is a preferred embodiment, it is understood that other embodiments may be adapted without falling outside the scope of the invention as described in the following claims.

What is claimed is as follows:

1. An improved switch assembly mounted within a recess of an air conditioning compressor for sensing re frigerant temperatures and pressures within its inlet portion comprising: a thin-walled hollow bellows having a sealed interior filled with a fluid which experiences volumetric changes with temperature variations; said bellows having a flexible end surface movable with respect to a fixed base portion of the bellows when the fluid therein expands and contracts in response to temperature and pressure variations; a mounting ring inserted into the recess in the compressor housing; said mounting ring having an inner bore through which said base portion of said bellows is secured inserted; radially extending slots in said mounting ring to permit refrigerant from the compressor inlet portion to flow around said bellows and to wash substantially all the bellows surface; an outer switch housing inserted into the recess over the mounting ring and held in sealing relation with respect to said compressor; said switch housing supporting an electrical contact which extends toward said movable end wall of said bellows; said contact being insulated from said switch housing to form a portion of an electrical indicator circuit through said contact, said bellows, and said mounting ring to the compressor housing when the flexible end of said bellows moves into engagement with said contact in response to high refrigerant temperature or low refrigerant pressure.

2. An improved switch assembly mounted within a recess of an air conditioning compressor for sensing refrigerant temperatures and pressures within its inlet portion comprising: a thin-walled hollow bellows having a sealed interior filled witha fluid which experiences volumetric changes with temperature variations; said bellows having a flexible end surface movable with respect to a fixed base portion of the bellows when the fluid therein expandsand contracts in response to temperature and pressure variations; a mounting ring inserted into the recess in the compressor housing; said mounting ring having an inner bore through which said base portion of said bellows is inserted; an annular groove formed in said inner bore of the mounting ring and being substantially the same diameter as said bellows so that the peripheral edge of said bellows extends therein and be grippingly engaged; radially extending slots in said mounting ring to permit refrigerant from the compressor inlet portion to flow around said bellows and to wash substantially all the bellows surface; an outer switch housing inserted into the recess over the mounting ring and to be held in sealingrelation with respect to said compressor to prevent refrigerant leakage thereby; a radially outward expandable retainer operably engaging a groove in the compressor housing thereby holding the mounting ring and outer switch housing within the recess; said outer switch housing supporting an electrical contact which extends toward said movable end wall of said bellows; said contact being insulated from said switch housing to form a portion of an electrical indicator circuit through said contact, said bellows, and said mounting ring to the compressor housing when the flexible end of said bellows moves into engagement with said contact in response to high refrigerant temperature or low refrigerant temperature or low refrigerant pressure.

3. An improved switch assembly mounted within a recess of an air conditioning compressor for sensing refrigerant temperatures and pressures within its inlet portion comprising: a thin-walled hollow bellows having a sealed interior filled with a fluid which experiences volumetric changes with temperature variations; said bellows having a flexible end surface movable with respect to a fixed base portion of the bellows when the fluid therein expands and contracts in response to temperature and pressure variations; a mounting ring inserted into the recess in the compressor housing; said mounting ring having an inner bore through'which said base portion of said bellows is inserted; an annular groove formed in said inner bore of the mounting ring and being substantially the same diameter as said bellows so that the peripheral edge of said bellows extends therein and is grippingly engaged; radially extending slots in said mounting ring to permit refrigerant from the compressor inlet portion to vflow around said bellows and to wash substantially all the bellows surface; an outer switch housing inserted into the recess over the mounting ring and held in sealing relation with respect to said compressor to prevent refrigerant leakage thereby; a radially outward expandable retainer operably engaging a groove in the compressor housing to hold the mounting ring and outer switch housing within the recess; said outer switch housing supporting an electrical contact which extends toward said movable end wall of said bellows; shim means between said mounting ring and said outer switch housing to space said movable end surface of said bellows a desired distance from said contact when said switch is assembled at a predetermined temperature and pressure; said contact being insulated from said switch housing to form a portion of an electrical indicator circuit through said contact, said bellows and said mounting ring to the compressor housing when the flexible end of said bellows moves into engagement with said contact in response to high refrigerant temperature or low refrigerant pressure within the compressor.

mg I UNITED STATES PATENT OFFICE CERTIFICATE OF' CORRECTION Patent No. 09,835 'Deted M y 7'. 1.97

Inventor-(s) Roy E. Watt It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, Line 51, "5" should read Column 4, Line 24, "122" should read --22-'-.

Column 5, Line 4, "iriserted" should be deleted; Line 36,

"be" should read -i'svSigned and sealed this 3rd day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN 'Attesting Officer Commissioner-of Patents 32 3 v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo- 3 809,835 Deted M y-7; 1.97

Inventofls) Roy E. Watt It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, Line 51, "5" should read Column 4, Line 24, "122" should read --22--.

Column 5, Line 4, "inserted" should be deleted; Line 36,

"be" should read --is- .Signed and sealed this 3rd day of December 1974.

(SEAL) Attest: v

McCOY M. GIBSON JR. C; MARSHALL DANN Arresting Officer Commissioner-of Patents 

1. An improved switch assembly mounted within a recess of an air conditioning compressor for sensing refrigerant temperatures and pressures within its inlet portion comprising: a thin-walled hollow bellows having a sealed interior filled with a fluid which experiences volumetric changes with temperature variations; said bellows having a flexible end surface movable with respect to a fixed base portion of the bellows when the fluid therein expands and contracts in response to temperature and pressure variations; a mounting ring inserted into the recess in the compressor housing; said mounting ring having an inner bore through which said base portion of said bellows is secured inserted; radially extending slots in said mounting ring to permit refrigerant from the compressor inlet portion to flow around said bellows and to wash substantially all the bellows surface; an outer switch housing inserted into the recess over the mounting ring and held in sealing relation with respect to said compressor; said switch housing supporting an electrical contact which extends toward said movable end wall of said bellows; said contact being insulated from said switch housing to form a portion of an electrical indicator circuit through said contact, said bellows, and said mounting ring to the compressor housing when the flexible end of said bellows moves into engagement with said contact in response to high refrigerant temperature or low refrigerant pressure.
 2. An improved switch assembly mounted within a recess of an air conditioning compressor for sensing refrigerant temperatures and pressures within its iNlet portion comprising: a thin-walled hollow bellows having a sealed interior filled with a fluid which experiences volumetric changes with temperature variations; said bellows having a flexible end surface movable with respect to a fixed base portion of the bellows when the fluid therein expands and contracts in response to temperature and pressure variations; a mounting ring inserted into the recess in the compressor housing; said mounting ring having an inner bore through which said base portion of said bellows is inserted; an annular groove formed in said inner bore of the mounting ring and being substantially the same diameter as said bellows so that the peripheral edge of said bellows extends therein and be grippingly engaged; radially extending slots in said mounting ring to permit refrigerant from the compressor inlet portion to flow around said bellows and to wash substantially all the bellows surface; an outer switch housing inserted into the recess over the mounting ring and to be held in sealing relation with respect to said compressor to prevent refrigerant leakage thereby; a radially outward expandable retainer operably engaging a groove in the compressor housing thereby holding the mounting ring and outer switch housing within the recess; said outer switch housing supporting an electrical contact which extends toward said movable end wall of said bellows; said contact being insulated from said switch housing to form a portion of an electrical indicator circuit through said contact, said bellows, and said mounting ring to the compressor housing when the flexible end of said bellows moves into engagement with said contact in response to high refrigerant temperature or low refrigerant temperature or low refrigerant pressure.
 3. An improved switch assembly mounted within a recess of an air conditioning compressor for sensing refrigerant temperatures and pressures within its inlet portion comprising: a thin-walled hollow bellows having a sealed interior filled with a fluid which experiences volumetric changes with temperature variations; said bellows having a flexible end surface movable with respect to a fixed base portion of the bellows when the fluid therein expands and contracts in response to temperature and pressure variations; a mounting ring inserted into the recess in the compressor housing; said mounting ring having an inner bore through which said base portion of said bellows is inserted; an annular groove formed in said inner bore of the mounting ring and being substantially the same diameter as said bellows so that the peripheral edge of said bellows extends therein and is grippingly engaged; radially extending slots in said mounting ring to permit refrigerant from the compressor inlet portion to flow around said bellows and to wash substantially all the bellows surface; an outer switch housing inserted into the recess over the mounting ring and held in sealing relation with respect to said compressor to prevent refrigerant leakage thereby; a radially outward expandable retainer operably engaging a groove in the compressor housing to hold the mounting ring and outer switch housing within the recess; said outer switch housing supporting an electrical contact which extends toward said movable end wall of said bellows; shim means between said mounting ring and said outer switch housing to space said movable end surface of said bellows a desired distance from said contact when said switch is assembled at a predetermined temperature and pressure; said contact being insulated from said switch housing to form a portion of an electrical indicator circuit through said contact, said bellows and said mounting ring to the compressor housing when the flexible end of said bellows moves into engagement with said contact in response to high refrigerant temperature or low refrigerant pressure within the compressor. 